1. Field of the Invention
The present invention generally relates to semiconductors. More specifically, the invention relates to increasing the breakdown voltage of a semiconductor device.
2. Background Art
Silicon semiconductor processing has evolved sophisticated operations for fabricating integrated circuits. As advancement in fabrication process technology continues, the operating voltage of the integrated circuits has reduced, but the operating voltage of auxiliary devices remains the same. Auxiliary devices are devices used in conjunction with integrated circuits and can include printers, scanners, disk drives, tape drives, microphones, speakers, cell phones and cameras to provide some examples.
Auxiliary devices can operate at voltages above the breakdown voltage of the transistors contained within the integrated circuit. As the operating voltage applied to a transistor increases, the transistor will eventually breakdown allowing an uncontrollable increase in current to pass through the devices. Breakdown voltage is the voltage level where this uncontrollable increase in current occurs. Examples of breakdown can include punch-through, avalanche breakdown, and gate oxide breakdown to provide some examples. Operating above the breakdown voltage for a significant duration reduces the lifetime of the transistor.
Techniques are currently available to increase the voltage at which breakdown occurs. These techniques can include the separate design of input-output circuits using a high voltage process, double diffused drain or other extended drain techniques, or the cascading of two individual transistors to provide some examples. These techniques often increase the fabrication cost by requiring additional process steps along with additional substrate masking.
What is needed is a metal oxide semiconductor field effect transistor (MOSFET) device and method for fabricating the same that addresses one or more of the aforementioned shortcomings of conventional MOSFET devices.